JP6990696B2 - Manufacturing method of paper or paperboard and use of composition - Google Patents

Description

The present invention relates to a method for producing paper or paperboard and the use of a composition for producing paper or paperboard, which is described in the preamble of the attached independent claim.

Recycled fiber materials are commonly used as raw materials for paper and paperboard. Recycled fiber materials contain many other substances in addition to fibers. When the recycled fiber material is formed into pulp, particulate foreign matter is separated from the pulp in the pulper or during screening (sieving). Some non-particulate matter is naturally retained on the fiber and does not significantly interfere with the process. Also, other substances such as sticky substances can be separated from the pulp during the screen treatment and removed from the process.

Recycled fiber materials typically include starch derived from the surface size of the paper or paperboard used as the pulp raw material. Starch typically has no or only a small amount of anionic charge, so it is hardly retained (yield) on the fiber. Moreover, starch cannot be effectively separated even during screen treatment due to its relatively small size. Therefore, the starch will remain in the water cycle of the pulping process or will be removed with the screen effluent sent to the wastewater treatment. Starch can also cause foaming in circulating water, as well as high levels of biochemical oxygen demand (BOD) and high levels of chemical oxygen demand (COD). Since starch is also a suitable nutrient for a variety of microorganisms, it also increases the risk of microbial growth during the process. Therefore, the issue of starch yield from recycled raw materials is an important, difficult but rewarding issue.

Some current concepts use two types of cationic polymers, but such two-type polymer systems are costly. In general, in order to achieve effects such as fixation, yield, strength, and drainage, various polymers with different molecular weights, charges, etc. are required for that purpose. Strength polymers are usually relatively low molecular weight and can only be produced as a solution. This is because the production method limits the molecular weight of the dry polymer to a high range. Dried polymers are usually used as flocculants due to their high molecular weight, and strong polymers usually do not improve dehydration and yield due to their low molecular weight.

In addition, a difficult task associated with recycled fiber materials is to achieve performance under high conductivity conditions. Linear cationic polymers cannot be added in increased amounts due to overflocculation and overcationization, resulting in poor texture, and thus the desired levels of yield, drainage and drainage. It has the disadvantage that strength is not always achieved. In addition, due to overaggregation and hypercationization, excessive foaming may occur during the manufacturing process. Especially when the conductivity is high, the performance deteriorates. This is because the higher the salt concentration, the more the ionic bond between the linear cationic polymer and the fiber is released.

An object of the present invention is to minimize or eliminate the shortcomings existing in the prior art.

An object of the present invention is to provide a method for producing paper, paperboard, or the like, which has improved starch yield and dehydration (water drainage).

In particular, it is an object of the present invention to provide a method for improving paper strength (paper strength) properties and starch yield using recycled or unbleached fiber materials, especially under high conductivity conditions. Is.

In particular, in order to achieve the above-mentioned objectives, the present invention is characterized by the contents presented in the characteristic portions of the attached independent claims.

Some preferred embodiments of the invention are described in the dependent claims.

The embodiments and advantages referred to herein relate to both methods and methods of use of the invention, if applicable, even if not specifically mentioned.

In a typical method for producing paper, paperboard, etc., this method uses recycled fiber as a raw material.
-Preparing pulp,
-(I) A copolymer of acrylamide and at least one cationic monomer containing at least 15 mol% of the cationic monomer as calculated from the total amount of the monomer, and (ii) containing at least two carboxyl groups. An aqueous treatment solution is prepared by dissolving a composition containing an ionic cross-linking agent containing a cross-linking agent having a carboxyl group: cationic monomer equivalent ratio of 1:20 to 1:0.5 in an aqueous solution such as water. To get,
-A method comprising adding the obtained treatment solution to the pulp and-forming the pulp into a fibrous web.

Now, surprisingly, a composition comprising a copolymer of acrylamide with at least one cationic monomer and an ionic crosslinker is obtained in the papermaking process and in terms of starch and colloid yield, drainage, and strength. It was found to improve the paper. These improvements result in a reversible three-dimensional (3D) ionic interaction between an ionic crosslinker with at least two carboxyl groups and the cationic monomer present in the copolymer of acrylamide and the cationic monomer. It is thought to be due to the structure. The formation of 3D structures is understood as one in which the viscosity of ionic crosslinked cationic polyacrylamide is reduced compared to, for example, linear, i.e., ionically non-crosslinked cationic polyacrylamide. be able to. The 3D structure facilitates high doses when in an aqueous environment without causing overaggregation and the resulting deterioration of the texture. That is, a polyionic complex is formed by the cationic polymer and the ionic cross-linking agent. Typically, the structure obtained by ionic interaction opens when the composition is diluted. However, when used in an environment with increased conductivity, or salt concentration, the presented copolymer remains in a compressed structure, increasing the cationicity of the polymer and increasing the amount added without causing overaggregation. Allows both to be done. In other words, under low conductivity conditions, after the polymer is added to the pulp, the structure of the polymer opens to produce large flocs. This floc is good for the yield of fibers and fillers, but not beneficial for paper strength (paper strength). Compositions comprising a copolymer of acrylamide with at least one cationic monomer and an ionic crosslinker are beneficial for strength, dehydration (water flow), starch and colloid yield, and fixation, thus water circulation in paper mills. Remains clean and clean. The three-dimensional structure obtained by ionic cross-linking is also beneficial for dehydration. In particular, using a pulp having a conductivity of at least 1 mS / cm, preferably at least 2.5 mS / cm, more preferably at least 3 mS / cm, even more preferably at least 3.5 mS / cm in the headbox stock will give strength. It can improve dehydration, starch and colloid yield, and fixation.

The composition used in the method according to the present invention contains an ionic cross-linking agent containing at least two carboxyl groups. As used herein, a carboxyl group means a -COOH group, whether in the protonated or deprotonated form. The equivalent ratio of carboxyl group: cationic monomer is 1:20 to 1:0.5, preferably 1:15 to 0.8, and more preferably 1:10 to 1: 1. Ionic cross-linking agents, in large amounts, excessively consume the cationic charge of the copolymer of acrylamide and at least one cationic monomer, and are strength aids, starch and colloid yield aids and / or dehydration aids. Performance is reduced. Moreover, higher amounts do not provide additional performance benefits and dilute the amount of polymer. When the amount of ionic crosslinker is small, the amount of ionic crosslinker is too small to form a 3D structure for the polymer, and its performance as a strength aid, starch and colloid yield aid and / or dehydration aid is poor. descend.

The copolymers and ionic crosslinkers of the composition form ionic crosslinked copolymers in aqueous solution, the ionic crosslinked copolymers having a standard viscosity in the range of 2.0 to 5.5 mPas. This was measured by a Brookfield DVI + viscometer from a 1.0% (w / w) sample in a 5.5% (w / w) NaCl solution at 25 ° C. The standard viscosity reflects the amount of ionic crosslinks present in the copolymer, and on the other hand, the magnitude of the molecular weight of the copolymer. In the absence of ionic crosslinkers, the standard viscosity of the same copolymer will be high. Standard viscosities of 2.0-5.5 mPas are required for papermaking, especially as strength aids, starch and colloid yield aids and / or dehydration aids, 3,000,000-20, It corresponds substantially to the weight average molecular weight MW in the range of ,000,000 g / mol.

According to one embodiment of the invention, the standard viscosity of the ion-crosslinked copolymer of acrylamide and at least one cationic monomer is a 5.5% (w / w) NaCl solution at 25 ° C. by Brookfield DVI + viscometer. When measured from a medium 1.0% (w / w) sample, it is in the range of 2.2 to 5.0 mPas, preferably 2.4 to 4.0 mPas, more preferably 2.5 to 3.5 mPas. .. These standard viscosities roughly correspond to the weight average molecular weight MW of acrylamide copolymers in the range of 4,000,000 to 15,000,000 g / mol or 5,000,000 to 9,000,000 g / mol. .. It has been found that this particular standard viscosity provides a clear improvement in dehydration and starch and colloid yields, as well as in the strength properties of the final or paperboard product.

According to one embodiment of the invention, the ionic crosslinker is citric acid, adipic acid, malonic acid, succinic acid, or any mixture thereof. The ionic cross-linking agent preferably contains citric acid and adipic acid. The majority of ionic crosslinkers are derived from citric acid. Citric acid is at least two functionally active or at pH 3.5-6, which is the pH required for a typical cationic polymer solution and which makes citric acid highly compatible with acrylamide copolymers. It provides a usable carboxyl group. This ionic crosslinker is available in powder form, which allows the production of compositions in dry particle form, as described below in the present application. In addition, adipic acid and citric acid are permitted for use in paper or paperboard grades that will come into contact with food or beverages. Furthermore, citric acid as a tribasic crosslinker increased to copolymers in that the viscosity of the ion-crosslinked cationic polyacrylamide solution was reduced compared to the dibasic crosslinker adipic acid. It has been demonstrated that it imparts structure. It was also observed that ionic crosslinkers, especially citric acid, protect the cationic groups of the polymer against hydrolysis in aqueous solution. In addition, citric acid minimizes or even inhibits microbial growth in aqueous solutions of the composition.

According to one embodiment of the invention, the amount of ionic crosslinker can be at least 2% by weight, preferably at least 2.5% by weight, or at least 3% by weight, and in some embodiments at least. It can be 3.5% by mass. According to one embodiment of the present invention, the amount of the ionic crosslinker is 2 to 20% by weight, preferably 2.5 to 20% by weight, more preferably 3.% by weight of the acrylamide copolymer represented as citric acid equivalent. It can be in the range of 5 to 20% by mass, and even more preferably 5.5 to 20% by mass. In some embodiments of the invention, the amount of ionic crosslinker can range from 3.5 to 15% by weight, more preferably 5.5 to 10% by weight.

According to the present invention, acrylamide copolymers contain at least 15 mol% of cationic monomers calculated from the total amount of monomers. According to a preferred embodiment of the invention, the acrylamide copolymer contains at least 20 mol%, preferably at least 30 mol%, more preferably at least 40 mol%, even more preferably at least 45 mol% of cationic monomer. The amount of cationic monomer in the copolymer realizes the desired three-dimensional structure by allowing the copolymer to interact with the ionic crosslinker. Furthermore, it was demonstrated that such higher cationic properties improve starch yield, filtrate turbidity, and strength as compared to, for example, 10 mol% cationic. The acrylamide copolymer can contain the cationic monomer in the range of 20 to 99 mol%, preferably 30 to 99 mol%, more preferably 40 to 80 mol%, still more preferably 45 to 65 mol%. However, if the amount of cationic monomer is too high, the cationic charge density of the resulting copolymer will also be too high, which may cause foaming and may reduce the fixation of other additives to the fiber. ..

The copolymer is obtained by polymerizing acrylamide with at least one cationic monomer. Examples of the cationic monomer include 2- (dimethylamino) ethyl acrylate (ADAM), [2- (acryloyloxy) ethyl] trimethylammonium chloride (ADAM-Cl), 2-dimethylaminoethyl methacrylate (MADAM), and [2- (Methylloyloxy) Ethyl] trimethylammonium chloride (MADAM-Cl), [3- (acryloylamino) propyl] trimethylammonium chloride (APTAC), [3- (methacryloylamino) propyl] trimethylammonium chloride (MAPTAC), or these. Any combination can be mentioned. Examples of the cationic monomer include 2- (dimethylamino) ethyl acrylate (ADAM), [2- (acryloyloxy) ethyl] trimethylammonium chloride (ADAM-Cl), and [2- (methacryloyloxy) ethyl] trimethylammonium chloride (MADAM). -Cl), [3- (acryloylamino) propyl] trimethylammonium chloride (APTAC), and [3- (methacryloylamino) propyl] trimethylammonium chloride (MAPTAC), or any combination thereof. Is preferable. The cationic monomer is more preferably selected from 2- (dimethylamino) ethyl acrylate (ADAM), [2- (acryloyloxy) ethyl] trimethylammonium chloride (ADAM-Cl), and any combination thereof. These monomers hydrolyze relatively easily, for example at high temperatures, so they are hydrolyzed, for example, during drying during production to form anionic groups, thereby forming three-dimensional structures through further ionic interactions. To promote. On the other hand, when dissolved in water, ionic crosslinkers, especially citric acid, protect the cationic groups of the polymer against further hydrolysis.

The acrylamide copolymer may also contain at least one structural unit derived from an anionic monomer (s), provided that its net charge is cationic at pH 7. Thus, the acrylamide copolymer can contain both cationic and anionic functional groups. According to one embodiment of the invention, the acrylamide copolymer contains 0.05 to 15 mol%, preferably 0.1 to 10 mol%, of the anionic monomer calculated from the total amount of the monomers.

Anionic monomers include unsaturated monos such as (meth) acrylic acid, maleic acid, fumaric acid, itaconic acid, aconitic acid, mesaconic acid, citraconic acid, crotonic acid, isocrotonic acid, angelic acid or tiglic acid. You can choose from dicarboxylic acids. The anionic monomer is preferably selected from (meth) acrylic acid and itaconic acid, and the anionic monomer is more preferably acrylic acid.

According to one embodiment of the invention, the composition comprises a copolymer of acrylamide obtained by a gel polymerization process. In gel polymerization, the monomers used are polymerized by using free radical polymerization in the presence of an initiator. The temperature at the start of the polymerization process may be less than 40 ° C and sometimes less than 30 ° C. Free radical polymerization of the monomers produces acrylamide copolymers, which are in gel form or highly viscous liquids. After gel polymerization, the obtained gel-form copolymer is pulverized by shredding or chopping, and further dried to obtain a dry granular copolymer. Depending on the reactor used, crushing or shredding may be performed in the same reactor where the polymerization is carried out. For example, the polymerization can be carried out in the first band (region) of the screw mixer and the resulting polymer can be disrupted in the second band of the screw mixer. It is also possible to perform crushing, shredding or other particle size adjustment with a processing device different from the reaction device. For example, the resulting water-soluble copolymer can be transferred from the second end of the reactor, which is a conveyor belt, through a rotary hole screen or the like, where the copolymer is crushed or shredded to a small particle size. After crushing or shredding, the ground copolymer is dried, milled to the desired particle size, and packaged for storage and / or transportation.

According to one preferred embodiment, the acrylamide copolymer is a linear copolymer at the end of the polymerization process. In other words, the acrylamide copolymer is not branched and does not contain permanent crosslinks. According to one embodiment, the polymerization of acrylamide with at least one cationic monomer is completely free of cross-linking agents that result in permanent cross-linking.

If the copolymer in the composition is obtained by gel polymerization, the ionic crosslinker may be added, for example, to the prepolymerized monomer and gels before or during grinding. Alternatively, the composition according to the invention can be obtained by mixing a copolymer in particle or powder form with at least a portion of an ionic crosslinker in particle or powder form. Mixing the two granular powders is also easy to carry out on an industrial scale, which can provide more freedom in the proportion of individual components.

According to one embodiment of the invention, the composition comprises 60-97% by weight, preferably 70-94% by weight, more preferably 78-90% by weight of acrylamide copolymer based on the dry solid content of the composition. include. The amount of copolymer in the composition is particularly high when the composition is in powder form. The high content of the polymer is beneficial in terms of the storage and transport properties of the composition.

The amount of residual cationic monomer in the composition may be up to 5000 ppm. The amount of residual acrylamide monomer in the composition may be up to 1000 ppm, preferably up to 700 ppm, more preferably up to 500 ppm. In particular, when the composition is used in the production of paper or paperboard grades that will come into contact with food or beverage, the amount of residual monomers is preferably as low as possible. In particular, when the composition is used in the production of paper or paperboard grades that come into contact with natural foods or beverages, it is preferable to minimize the amount of residual monomers.

According to one embodiment of the invention, the composition can be in the form of a water-soluble dry powder. The term "water-soluble" should be understood in the context of this application that the composition and its constituents are completely miscible with water. When mixed with excess water, the composition is preferably completely soluble and the resulting solution preferably contains essentially no separate independent particles or granules. Excess water means that the resulting solution does not become a saturated solution with respect to any of the components present.

According to one embodiment of the present invention, the water content of the dry powder of the present composition can be up to 15% by mass. Typically, the water content is 3-15% by weight, and in some embodiments it can typically be 5-12% by weight.

According to one embodiment of the invention
(I) A copolymer of acrylamide and at least one cationic monomer, which contains at least 15 mol% of the cationic monomer calculated from the total amount of the monomers, and
(Ii) An ionic cross-linking agent containing at least two carboxyl groups, wherein the equivalent ratio of carboxyl group: cationic monomer is 1: 20 to 1: 0.5, preferably 1: 15 to 0.8, more preferably. Uses a composition containing a cross-linking agent having a ratio of 1:10 to 1: 1 as a drying strength agent in the production of paper, paperboard, or the like.

According to another embodiment of the invention
(I) A copolymer of acrylamide and at least one cationic monomer, which contains at least 15 mol% of the cationic monomer calculated from the total amount of the monomers, and
(Ii) An ionic cross-linking agent containing at least two carboxyl groups, wherein the equivalent ratio of carboxyl group: cationic monomer is 1: 20 to 1: 0.5, preferably 1: 15 to 0.8, more preferably. Uses a composition containing a cross-linking agent of 1:10 to 1: 1 as a drainage agent and / or a yield agent for starch and colloid in the production of paper or paperboard. It is preferable not to use other synthetic organic dehydration aids (drainage aids). That is, the paper or paperboard manufacturing method does not include other organic dehydration aids.

The composition according to the present invention can be used for producing kraft paper, liner board, test liner, fluting, bag paper, backing white chip ball (WLC), paperboard for paper tubes, or paperboard for folding boxes (FBB). .. Paperboard can have a basis weight of 120-500 g / m ² and is based on 100% primary fiber, 100% recycled fiber, or a usable mixture between primary fiber and recycled fiber. be able to.

According to a method for producing paper or paperboard, which is a process using recycled fibers as a raw material, the composition according to the present invention is dissolved in an aqueous solution such as water, whereby an aqueous treatment solution is obtained. Add the treatment solution to the pulp. According to a preferred embodiment of the method, the pulp is recycled paper, board or the like pulped in pulper and / or unbleached kraft pulp and / or unbleached. It contains at least 50% by mass of dry fibre furnish , such as semi-chemical pulp, preferably recycled paper, board or the like, which is pulped in pulper.

According to one preferred embodiment of the invention, the pulp in the headbox stock is at least 1 mS / cm, preferably at least 2.5 mS / cm, more preferably at least 3 mS / cm, even more preferably at least 3. It has a conductivity of 5 mS / cm. Typically, the pulp has a conductivity of up to 15 mS / cm, 10 mS / cm, 8 mS / cm, 6 mS / cm or 5.5 mS / cm in the headbox stock. According to one embodiment of the invention, the pulp conductivity in the headbox stock is 1-15 mS / cm, preferably 2.5-15 mS / cm, more preferably 3-15 mS / cm, even more preferably 3. It can vary in the range of .5 to 15 mS / cm. In particular, it has conductivity in the range of 1-10 mS / cm, preferably 2.5-10 mS / cm, more preferably 3-10 mS / cm, even more preferably 3.5-10 mS / cm in headbox stock. When pulp is used, strength, dehydration (strain) property, starch and colloid yield, and fixability are improved. In some embodiments of the invention, the pulp conductivity in the headbox stock is 1-10 mS / cm, preferably 2.5-8 mS / cm, more preferably 3-6 mS / cm, even more preferably 3. It is in the range of 5.5 to 5.5 mS / cm.

According to one embodiment of the invention, the pulp is measured at the outlet pump point of the pulp or waste paper storage, preferably the pulp or waste paper storage, and the dry total solids content. Is included in an amount of at least 0.5% by weight, preferably at least 2% by weight, more preferably at least 3% by weight, and even more preferably 4% by weight. The starch content of the pulp is measured after the pulp storage or waste paper storage and is based on the dry total solids, for example 1-20% by weight, preferably 2-10% by weight, preferably 4%. It can be in the range of 8% by mass.

According to one embodiment of the invention, the composition is an amount of 50-1000 dry g / t dry pulp, preferably 150-900 dry g / t dry pulp, more preferably 300-800 dry g / t dry pulp. Used in.

According to one embodiment of the invention, the resulting treatment solution is added to the fiber pulp after the final shearing step and in front of the paper machine or paper machine headbox. Therefore, the treatment solution is added to the dilute fiber stock having a consistency of less than 3% (<), preferably less than 2.5%, more preferably less than 2%. Adding to a dilute stock is particularly advantageous for dehydration (drainage). According to one embodiment of the invention, the resulting treatment solution is added to the pulp fraction from the pulper. This is because the copolymer in the treatment solution easily comes into contact with starch and fibers. In this way, the starch yield to the paper web can be effectively improved.

It is also possible to add at least one amylase enzyme inhibitor and / or biocide to pulp and / or waste paper for the purpose of controlling microbial activity in the process. Enzyme inhibitors and / or biocides reduce starch degradation due to microbial activity. In this way, more starch is available for interaction with the compositions according to the invention.

Biocides and / or amylase enzyme inhibitors can be added into the pulper or into the flow within the process, eg, pulp stream or process water stream. The biocide and / or amylase enzyme inhibitor is preferably added during the process prior to the pulp storage tower or silo located after the pulp enrichment step. Biocides and / or enzyme inhibitors can be added to the pulp in the pulper or prior to concentration of the screened pulp. According to one preferred embodiment of the invention, the biocide or amylase enzyme inhibitor is added to the pulp stream within 2 hours from the moment the pulp stream exits the pulper. In addition, biocides or amylase enzyme inhibitors can be added to the pulp between the inlet of the pulper and the enrichment treatment of the screened pulp. Early addition of biocides or amylase enzyme inhibitors minimizes further degradation of starch and improves coagulation and floculation of low molecular weight starch, thereby increasing the yield of starch to recycled fibers. It is preferable because it can be improved. It is possible to add the biocide and / or the amylase enzyme inhibitor at only one location in the biocide supply position. Alternatively, the biocide and / or amylase enzyme inhibitor can be added at several separate supply positions at intervals from each other. This allows the biocide to be added by targeting known problems during the process. It is also possible to add the biocide at the first supply position and the amylase enzyme inhibitor at another second supply position.

The biocide may be any suitable biocide that reduces the number of viable bacteria and / or microorganisms in the process by at least 80%. Similarly, the amylase enzyme inhibitor can be any of the substances that inhibit the formation of the amylase enzyme or inactivate the amylase enzyme, and may be, for example, a zinc inhibitor. The amylase enzyme inhibitor is preferably any suitable inhibitor that reduces starch degradation by at least 20% under process conditions.

According to one embodiment of the invention, the biocide is an oxidative biocide or a non-oxidative biocide.

According to one embodiment of the invention, biocides include oxidative biocides such as sodium hypochlorite, hypobromous acid, chlorine dioxide and the like; halogenated hydantoins such as bromochloro-dimethylhydantoin and the like. It can be selected from the group comprising a partially halogenated hydantoin such as monochloro-dimethylhydantoin; a haloamine such as chloramine or bromamine; or a mixture thereof. Suitable for use in one embodiment of the invention, haloamines are ammonium hypochlorite sources such as ammonium sulfate, ammonium chloride, ammonium bromide, ammonium phosphate, ammonium nitrate, or any other ammonium salt containing urea. It can be formed by combining with an oxidizing agent such as. The biocide can be added continuously throughout the treated portion of the system so that the total active chlorine concentration is about 0.1-5 ppm. It is more preferable that the active chlorine concentration of the treated portion of the system system is about 0.75 to 2 ppm. It is also possible to add biocides by using slug administration. Slag administration refers to periodic or batch administration of the biocide to the process as opposed to continuous administration. Typically, the slag dose is 1-10 ppm, preferably 3-7 ppm. The slugs are preferably supplied about 6 to 24 times a day for about 3 to 30 minutes each, more preferably about 12 to 24 times a day for about 5 to 15 minutes each.

In embodiments of the present invention, the non-oxidizing killing agents include glutaaldehyde, 2,2-dibromo-3-nitrilopropionamide (DBNPA), 2-bromo-2-nitropropane-1,3-diol (Bronopol). ), Quaternary ammonium compound, carbamate, 5-chloro-2-methyl-4-isothiazolin-3-one (CMIT), 2-methyl-4-isothiazolin-3-one (MIT), 1,2-dibromo- 2,4-dicyanobutane, bis (trichloromethyl) sulfone, 2-bromo-2-nitrostyrene, 4,5-dichloro-1,2-dithiol-3-one, 2-n-octyl-4-isothiazolin-3 -On, 1,2-benzisothiazolin-3-one, orthophthaldehyde, quaternary ammonium compound (= "quats"), such as n-alkyldimethylbenzylammonium chloride, didecyldimethylammonium chloride (DDAC) ) Or alkenyldimethylethylammonium chloride, guanidine, biguanidine, pyrithione, 3-iodopropynyl-N-butylcarbamate, phosphonium salt, eg, tetrakishydroxymethylphosphonium sulfate (THPS), dasomet, 2- (thiocyanomethylthio) benzothiazole, Methylbisthiocyanate (MBT) and combinations thereof can be mentioned. Suitable non-oxidizing biocides include glutaraldehyde, 2,2-dibromo-3-nitrilopropionamide (DBNPA), 2-bromo-2-nitropropane-1,3-diol (Bronopol), quaternary. It is selected from ammonium compounds, carbamate, 5-chloro-2-methyl-4-isothiazolin-3-one (CMIT) and 2-methyl-4-isothiazolin-3-one (MIT).

Experimental Examples Unless otherwise stated, data in percentages are always weight percent.

The standard viscosity was measured by the following method.
First, the salt solution is prepared by dissolving sodium chloride (525 g) in deionized water (3000 g) in a beaker equipped with a magnetic bar and a magnetic stirrer. The mixture is stirred with a magnetic stirrer at maximum speed until the sodium chloride is completely dissolved.

Add deionized water (200.0 g) to the beaker. Place the magnetic stirrer bar in a beaker and stir with the highest speed magnetic stirrer. Add 0.330 g of cationic polyacrylamide polymer to the beaker for 15 seconds with stirring. The mixture is stirred at maximum speed for 5 minutes using a magnetic stirrer and then at 350 rpm for 25 minutes. A salt solution (117.5 g, 15% (w / w) NaCl) is added to the beaker and the mixture is stirred for 5 minutes. The formed solution is filtered through a stainless steel mesh sieve with a diameter of 10 cm and a diameter of 250 microns. The viscosity of the filtered solution (1.0% (w / w) sample in 5.5% (w / w) NaCl solution) was then applied at 25 ° C. with UL adapters ULA-35Z and YULA-15Z ULA spindles. Measure at maximum rotational speed using a Brookfield DVI + viscometer. The sample amount used for viscosity measurement is 16 ml.

The solution viscosity was measured by the following method.
Cationic polyacrylamide (2.50 g) was dissolved in water (497.5 g) to prepare a 0.5% CPAM solution. The viscosity was measured by a Brookfield DV1 equipped with a small sample adapter at a maximum rotation speed of 25 ° C. using a spindle S31.

Example 1 General procedure for the production of a copolymer of acrylamide and a cationic monomer A acrylamide solution (50% by weight) and an ADAM-Cl solution (80% by weight) are placed in a reactor at a predetermined molar ratio for each polymer product. Charge. The pH is adjusted to about 2.5-4.5 by adding 1% by weight of adipic acid to the total amount of the monomer. Other chemicals such as chain transfer agents, chelating agents, and heat initiators are added to the monomer mixture. The solution is then purged with nitrogen gas. The redox pair initiator system is injected into the polymerization reactor to initiate polymerization. The polymerization reaction results in a cationic polyacrylamide gel. The gel is dried to finally obtain a powder or particles. The polymer composition has a dry content of about 95-98% by weight. The physical characteristics of the polymer are measured using the obtained powder.

Example 2 Composition of ionic cross-linking copolymer of acrylamide and cationic monomer A composition of citrate or adipic acid added after polymerization as a copolymer of acrylamide and a cationic monomer and an ionic cross-linking agent is cationic in water. It is prepared by adding polyacrylamide powder and stirring at 25 ° C. for 60 minutes with a magnetic stirrer, then adding acid to the polymer solution and stirring with a magnetic stirrer for 15 minutes. Examples of polymer solutions are shown in Table 1. CPAM in the solution is CPAM 49 mol% ADAM-Cl, dry content 95%. The charge density of 49 mol% CPAM is 3.7 meq / g polymer and the total cationic charge in 0.5% solution is 18.5 meq / liter. The MW of citric acid is 19.2 g / mol. Citric acid is a tribasic acid, and each mole of citric acid contains 3 equivalents of potential anion. Thus, for example, 0.22 g of citric acid can contain anionic charges up to 3.4 meq. Table 2 shows the properties of each solution and the equivalent ratio of carboxyl group: cationic monomer. These solutions are used in Application Example 1.

Table 1 CPAM (49 mol% ADAM-Cl) non-crosslinked reference example and ion-crosslinked composition sample (CS) solution (2.6 g CPAM with a dry content of 95% in 500 ml water, ie 0.5 mass% CPAM solution). Preparation and properties. The cationic charge of each sample was 18.5 meq / liter. For each sample, CPAM was polymerized in the presence of the same amount of adipic acid, 1% (w / w) CPAM, taking into account the equivalent ratio. Solution viscosities and standard viscosities were measured as defined above.

From Table 1, it can be seen that the ion-crosslinked CPAM sample has a lower standard viscosity and a lower solution viscosity than the non-crosslinked reference example. Further, the decrease in the viscosity of the solution is more remarkable as the relative amount of the cross-linking agent is larger, and even if the equivalent ratio is the same, when the tribasic cross-linking agent is used, it is compared with the case of the divalent cross-linking agent. It can be seen that a greater decrease in viscosity can be obtained.

Application example
Pulp preparation
European test liner paperboard (board) was used as a raw material. This test liner contains about 5% surface size starch. This starch was an enzymatically degraded natural cornstarch. Diluted water was made by adjusting the Ca ²⁺ concentration of tap water to 520 mg / l with CaCl ₂ and adjusting the conductivity to 4 mS / cm with NaCl. The test liner paperboard was cut into 2 x 2 cm squares. 2.7 liters of diluted water was heated to 85 ° C. The test liner pieces were moistened in 2% diluted water for 5 minutes prior to dissociation. The slurry was dissociated at 30,000 rpm in the Brit jar dissociator. Diluting water was added to dilute the pulp to 0.5%.

DDA test A DDA (Dynamic Drainage Analyzer) (AB Akribi Kemikonsulter, Sweden) was used to measure yield and dehydration (draining). 500 ml of pulp was used for each test point. Pulp was poured into the DDA 30 seconds before dehydration and the DDA stirrer was adjusted to 1000 rpm. The polymer was added 10 seconds before dehydration. Stirring was stopped 2 seconds before dehydration. For 30 seconds after the start of dehydration, the degree of vacuum was set to 300 mBar and the wire opening was 0.25 mm.

The drainage time was recorded and the filtrate turbidity and PCD were immediately measured. The DDA sheet was weighed and pressed at 4 bar for 1 minute with a sheet press with two sheets of plotter paper on both sides. Sheets from the wire were dried to absolute dryness (abs dry) in a Lorenzt & Wettre hot plate dryer for the purpose of yield calculation. ISO9895 compliant SCT measurements were repeated 6 times for each DDA sheet. The results are shown as an index based on the basis weight of the DDA sheet (sheet dry mass / area).

The yield of starch derived from recycled pulp (in this case, nonionic degraded starch derived from the coating of test liner paperboard) was determined from the DDA filtrate. This determination method is also suitable for measuring the amount of starch in pulp. 25 ml of filtrate (or pulp) was added to 10 ml of 10% by weight HCl. The mixture was stirred with a magnetic stirrer for 10 minutes and filtered by gravity in a funnel using black ribbon filter paper. 1 ml of the filtered mixture was added to 8.5 ml of water. 0.5 ml of an iodine reagent consisting of 7.5 gKI / l + 5 g / lI ₂ was added, and 1 minute after the iodine solution was added, the absorbance value was measured at 610 nm using a Hach Range DR900 spectrophotometer. Zero adjustment of the spectrophotometer was performed using the sample before iodine addition. A calibrated formula for starch content was prepared using C * film 07311 nonionic biodegradable starch as a reference. A blank test was performed on the absorbance of the HCl-iodine solution to subtract the baseline absorbance from the results. Starch yield was calculated as (pulp starch-sulfate starch) / pulp starch x 100%. Also, starch reduction was calculated as (zero test filtrate starch-sulfate starch) / filtrate starch x 100%.

Application example 1
Table 2 shows the test chemical substances used in this example. Table 3 shows the administration and administration time of the chemical substance. Citric acid was added to CPAM upon dissolution. The ion-crosslinked CPAM samples labeled CS1, CS2 and CS3 are the same as in Table 1. The administration time is the time before dehydration.

From Table 4, it can be understood that CPAM flocculant is essential for obtaining improved dehydration performance and that ionic cross-linking does not interfere with the dehydration performance of CPAM. When the three-component program product of PAC, silica and CPAM was used, especially when the three-component program product was used together with the ion-crosslinked CPAM of the present invention, a remarkable improvement in starch yield was observed as compared with the case of CPAM alone. Be done. It is not surprising that SCT intensity decreases as the use of CPAM increases overall yield and aggregation. The ion-crosslinked CPAM of the present invention achieves the same improvements in overall yield and dehydration (drainage) as non-crosslinked CPAM in both programs, but does not reduce SCT intensity and is only slight in test number 7. However, it can even be seen that SCT has increased. Furthermore, it can be seen that the starch yield increases as the amount of the ionic crosslinker increases. A more structured, ion-crosslinked CPAM would be an excellent option for capturing degraded nonionic starch resulting from the surface size of the test liner board.

Application example 2
The composition of the ion-crosslinked copolymer used in this example was prepared as described in Example 2. The characteristics are shown in Table 5. Table 6 shows the administration time, dose and test results before dehydration.

It can be seen from Table 6 that the ion-crosslinked CPAM with higher cationicity resulted in higher SCT intensity and starch reduction compared to CPAM with 10 mol% cationicity.

Application example 3
The same sample as in the previous example shown in Table 5 was used. The dosing time and dose before dehydration are presented in Table 7, and the test results are shown in Table 8.

From Table 8, ion-crosslinked CPAMs (Test Nos. 27-32) with greater than 15 mol% cations have higher starch reduction and lower turbidity than CPAMs with only 5 mol% cations. You can see that it has been realized. In addition, the ion-crosslinked CPAM with higher cationic properties achieved improved dehydration and yield even at lower doses. Furthermore, it can be seen that when the relative amount of carboxyl to the cationic monomer is high, the drainage time is shortened and the turbidity is reduced, which suggests an improvement in the colloidal yield.

Claims (12)

It is a manufacturing method of paper or paperboard , etc.
-(I) A copolymer of acrylamide and at least one cationic monomer containing at least 15 mol% of the cationic monomer calculated from the total amount of the monomers, and (ii) containing at least two carboxyl groups. A step of dissolving a composition containing an ionic cross-linking agent containing a cross-linking agent having a carboxyl group: cationic monomer equivalent ratio of 1:20 to 1:0.5 in an aqueous solution to obtain an aqueous treatment solution.
-The step of adding the obtained treatment solution to the pulp, where the pulp is a dried fiber of recycled paper or recycled paperboard and / or unbleached kraft pulp and / or unbleached semi-chemical pulp pulped in pulper. It contains at least 50% by mass of the finished paper material and has a conductivity in the range of 1-15 mS / cm in the headbox stock, and-forms the pulp to which the treatment solution is added into the fibrous web. A method characterized by including steps. The first aspect of the present invention, wherein the copolymer of acrylamide contains at least 20 mol%, preferably at least 30 mol%, more preferably at least 40 mol%, and even more preferably at least 45 mol% of the cationic monomer. the method of. The cationic monomer of the copolymer is characterized by being selected from 2- (dimethylamino) ethyl acrylate (ADAM), [2- (acryloyloxy) ethyl] trimethylammonium chloride (ADAM-Cl), and combinations thereof. The method according to claim 1 or 2 . Claims 1 to 3 are characterized in that the equivalent ratio of the carboxyl group: cationic monomer in the ionic cross-linking agent is preferably 1:15 to 0.8, more preferably 1:10 to 1: 1. The method described in any one of the above. The method according to any one of claims 1 to 4 , wherein the copolymer further contains an anionic monomer, provided that the net charge of the copolymer of acrylamide is cationic at pH 7. The method according to any one of claims 1 to 5 , wherein the composition is in the form of a dry powder. The amount of the ionic cross-linking agent is 2 to 20% by mass, preferably 2.5 to 20% by mass, more preferably 3.5 to 20% by mass, still more preferably the amount of the acrylamide copolymer expressed as citric acid equivalent. The method according to any one of claims 1 to 6 , wherein is in the range of 5.5 to 20% by mass. The pulp measures starch in a pulp or waste paper reservoir and is at least 0.5% by weight, preferably at least 2% by weight, more preferably at least 3% by weight, based on the total dry solids. The method according to any one of claims 1 to 7 , wherein the method is more preferably contained in an amount of at least 4% by mass. Claims characterized in that the composition is used in an amount of 50-1000 dry g / t dry pulp, preferably 150-900 dry g / t dry pulp, more preferably 300-800 dry g / t dry pulp. Item 8. The method according to any one of Items 1 to 8 . The method according to any one of claims 1 to 9 , wherein the treatment solution obtained is added after the final shearing step and in front of the paper machine or the head box of the paper machine. .. The method according to any one of claims 1 to 10 , wherein at least one amylase inhibitor and / or biocide is added to pulp and / or waste paper. The method according to any one of claims 1 to 11 is used for producing kraft paper, liner board, test liner, fluting, bag paper, backing white chip ball, paperboard for paper tubes, or paperboard for folding boxes. Method .